I'm skeptical, not at the power efficiency claims, but that the result will be cellphones that last longer. They are designed to last a day or two. Everyone will just shrink batteries and increase workloads until cellphones last as long as they do now.

https://hardware.slashdot.org/story/21/12/16/2332227/ibm-and-samsung-say-their-new-chip-design-could-lead-to-week-long-battery-life-on-phones